In the past, the control of vacuum pan boiling has always been made difficult by the fact that no simple means existed for the direct measurement of supersaturation and crystal content in massecuites. These are the two prime variables to be controlled and until they can be measured, it is not possible to achieve optimal control of vacuum pan boiling. In the past, measurement of conductivity, viscosity, elevation of boiling point, density and dielectric constant have been used with various degrees of success to control vacuum pans.
In raw sugar factories, electrical conductivity is the most common of these parameters used for pan control. This measurement, however, suffers from a few serious drawbacks:
(1) The conductivity measurement is very dependent on the purity of the boiling massecuite, particularly when the purity is greater than 85.
(2) The conductivity measurement depends on crystal content and mother liquor purity and brix of the massecuite and it is possible to have two different qualities of massecuite having the same conductivity.
(3) When used in continuous vacuum pans, conductivity probes are subject to extensive scaling, which has a considerable effect on the reading.
It is an object of the present invention to provide a method and apparatus for measuring conductivity and di-electric constant in order to obtain a more exact control of the conditions of massecuite.